{ "id": 6860, "title": "Probabilities not summing up to 1", "url": "/competitions/galaxy-zoo-the-galaxy-challenge/discussion/6860", "author_name": "", "post_date": "2014-01-17T17:25:57.307Z", "votes": null, "comment_count": 6, "views": 2224, "content": "

This is probably a misunderstanding on my part but shouldn't the sum of probabilities at every level in the decision tree sum to 1? It doesn't seem to adhere to this rule.

\n

Thanks

", "messages": [ { "id": "37517", "postDate": "01/17/2014 17:25:57", "content": "

This is probably a misunderstanding on my part but shouldn't the sum of probabilities at every level in the decision tree sum to 1? It doesn't seem to adhere to this rule.

\n

Thanks

", "rawMarkdown": "", "votes": null }, { "id": "37527", "postDate": "01/17/2014 19:24:40", "content": "

The probabilities are reweighted by the probability of the path(s) that lead to this particular node in the tree. As an example, question 2 is asked when the user answers 'feature or disk' (answer 2) to question 1, so the probabilities of the answers to question 2 will sum up to the probability of question 1, answer 2.

\n

The only exception to this rule is question 6, where the probabilities always sum to 1, even when some users answered 'star or artifact' (answer 3) to question 1. This was apparently done because the number of people that give answer 3 is usually negligible.

\n

I posted some Python code to check the label constraints earlier, you can find all the relations between the probabilties of different answers in there as well.

", "rawMarkdown": "", "votes": null }, { "id": "37563", "postDate": "01/18/2014 12:25:09", "content": "

Great, that makes sense now. Thanks a lot :)

", "rawMarkdown": "", "votes": null }, { "id": "37836", "postDate": "01/23/2014 22:01:44", "content": "

I didn't see this post earlier, so I had posted another note on how the sum of probabilities to end the process is greater than 1 (and thus greater than to start the process) !.

\n

 

\n

It seems wrong (to me) that 6.1 + 6.2 = 1.0, when 1.3 is often different from zero !

\n

So, 6.1 + 6.2 + 1.3, which is the probability to end the process, is greater than one.

\n

I agree with Bary on this one.

\n

 

\n

Eric

", "rawMarkdown": "", "votes": null }, { "id": "38288", "postDate": "02/03/2014 00:50:57", "content": "

.

", "rawMarkdown": "", "votes": null }, { "id": "38782", "postDate": "02/14/2014 12:27:06", "content": "

Please read the similar thread Is question 6 also answered for stars/artifacts (answer 1.3)? before continuation. It was satisfactory for me.



 

\n

 

", "rawMarkdown": "", "votes": null }, { "id": "39110", "postDate": "02/19/2014 21:49:14", "content": "

I have also written a helper function for normalizing the output probability according to the decision tree tailored to this problem. (Thank sedielem for the original code)

\n

But in my situation, that does not help decreasing the RMS that much as I originally expected

", "rawMarkdown": "", "votes": null } ], "comments": [ { "id": 37527, "author_name": "sedielem", "author_url": "", "post_date": "01/17/2014 19:24:40", "content": "

The probabilities are reweighted by the probability of the path(s) that lead to this particular node in the tree. As an example, question 2 is asked when the user answers 'feature or disk' (answer 2) to question 1, so the probabilities of the answers to question 2 will sum up to the probability of question 1, answer 2.

\n

The only exception to this rule is question 6, where the probabilities always sum to 1, even when some users answered 'star or artifact' (answer 3) to question 1. This was apparently done because the number of people that give answer 3 is usually negligible.

\n

I posted some Python code to check the label constraints earlier, you can find all the relations between the probabilties of different answers in there as well.

", "votes": null, "replies": [] }, { "id": 37563, "author_name": "mohamedabdelbary", "author_url": "", "post_date": "01/18/2014 12:25:09", "content": "

Great, that makes sense now. Thanks a lot :)

", "votes": null, "replies": [] }, { "id": 37836, "author_name": "", "author_url": "", "post_date": "01/23/2014 22:01:44", "content": "

I didn't see this post earlier, so I had posted another note on how the sum of probabilities to end the process is greater than 1 (and thus greater than to start the process) !.

\n

 

\n

It seems wrong (to me) that 6.1 + 6.2 = 1.0, when 1.3 is often different from zero !

\n

So, 6.1 + 6.2 + 1.3, which is the probability to end the process, is greater than one.

\n

I agree with Bary on this one.

\n

 

\n

Eric

", "votes": null, "replies": [] }, { "id": 38288, "author_name": "tanstaafl", "author_url": "", "post_date": "02/03/2014 00:50:57", "content": "

.

", "votes": null, "replies": [] }, { "id": 38782, "author_name": "hynekcernoch", "author_url": "", "post_date": "02/14/2014 12:27:06", "content": "

Please read the similar thread Is question 6 also answered for stars/artifacts (answer 1.3)? before continuation. It was satisfactory for me.



 

\n

 

", "votes": null, "replies": [] }, { "id": 39110, "author_name": "stevenwudi", "author_url": "", "post_date": "02/19/2014 21:49:14", "content": "

I have also written a helper function for normalizing the output probability according to the decision tree tailored to this problem. (Thank sedielem for the original code)

\n

But in my situation, that does not help decreasing the RMS that much as I originally expected

", "votes": null, "replies": [] } ], "raw_markdown_by_id": { "37517": "", "37527": "", "37563": "", "37836": "", "38288": "", "38782": "", "39110": "" }, "source": "meta" }